1. Field of the invention
This invention relates to a resin composition and a surface-treated inorganic filler, and more particularly, to a styrene-based resin composition that is available for heat resistant parts in automobiles, domestic electric appliances and electric and electronic devices, or heat resistant structural materials for industrial use, and an inorganic filler which is surface treated and is suitable for filling in a styrene-based polymer.
2. Description of the Related Arts.
A styrene-based polymer having a syndiotactic configuration shows excellent mechanical strength, heat resistance, solvent resistance and electric characteristics compared with a styrene-based polymer having an atactic configuration. Therefore, in recent years, various studies to formulate a styrene-based polymer having a syndiotactic configuration to improve heat resistance or a solvent resistant thermoplastic resin, have been carried out. For example, Japanese Patent Application Laid-Open No. 257950/1987, discloses a thermoplastic resin composition to which a polystyrene having a syndiotactic configuration is added in order to improve the heat resistance of the thermoplastic resin. However, while the composition obtained certainly has an improved heat resistance, its tensile strength and elongation performance are markedly lowered in a composition with a resin which has less affinity with polystyrene. As a result, the composition is not preferred depending on the use thereof due to its poorer physical properties. Furthermore, there are problems in not only lowering in physical properties but also in its appearance, such as peeling of the surface layer of a molded product.
In order to overcome the above problems, the present inventors previously proposed a technique in which a specific block copolymer is added to improve affinity and dispersibility when blending a styrene-based polymer having a syndiotactic configuration with a thermoplastic resin, which has less affinity for the styrene-based polymer. For example, a polyamide resin has been known to have excellent moldability and heat resistance, and sufficient rigidity. Therefore, it has been used as a molding material for various products such as domestic materials, and parts of electric and mechanical instruments. However, the polyamide resin has a disadvantage in terms of water resistance although it has the excellent properties as mentioned above.
An attempt has been made to overcome the above disadvantage by adding the above styrene-based polymer to the polyamide. When the above styrene-based polymer is blended with the polyamide, a block copolymer of polystyrenepolyamide is added thereto. In addition, when the above styrene-based polymer is blended with a polybutyreneterephthalate, a block copolymer of a polystyrene-polybutyreneterephthalate is added thereto. That is, this technique adds a block copolymer comprising a polystyrene and a resin to be blended with the polystyrene as a modifier. According to this technique, modification effects can be obtained to some extent, and mechanical properties are particularly improved compared with that disclosed in Japanese Patent Publication Laid-Open No. 257950/1987.
However, according to this technique, it is necessary to prepare a block copolymer previously when a blended material is prepared so there is a disadvantage in that complicated procedures are required for industrial production.
On the other hand, an attempt has been made by formulating an inorganic filler such as glass fiber to various synthetic resins to improve mechanical properties, particularly rigidity and heat resistance. However, a styrene-based polymer has insufficient adhesiveness with an inorganic filler, so various investigations have been made concerning additives to improve adhesiveness or a surface treating agent of the inorganic filler. As a result, surface treating agents have been developed such as those in which various aminosilane compounds are combined with resins of polyester, urethane, epoxy, acryl and vinyl acetate, and additives such as maleic acid anhydride-styrene copolymer. More specifically, there have been known a silane coupling agent for glass fiber which is used as a surface treating agent, and a styrene/maleic anhydride-styrene/glass fiber composition as a composition in which an additive is formulated (Japanese Patent Application Laid-Open No. 161836/1980 and Japanese Patent Publication No. 19097/1974). However, the improvements brought about by these have also been inadequate.
In addition, Japanese Patent Publications Laid-Open No. 257948/1987 and No. 182344/1989, proposed resin compositions in which an inorganic filler is added to a syndiotactic polystyrene, and an inorganic filler is added to a syndiotactic polystyrene/a thermo-plastic resin and/or a rubber, respectively, to improve heat resistance and mechanical properties. However, the adhesiveness of the syndiotactic polystyrene and the inorganic filler is also insufficient in these compositions, so improvements have been desired.
That is, in conventional attempts in which the surfaces of various inorganic fillers and additives are treated with various surface treating agents, adhesiveness with a styrene-based polymer, particularly with a syndiotactic polystyrene is insufficient. In particular, impact resistance is low so an improvement in impact resistance has been desired.